You've already got an open source Winamp if you're using the likes of xmms, qmmp, Audacious or anything else that effectively loads classic style skins (not that they tend to get it spot in) so does it really matter what the state of Winamp vs it's source code is...? I'd say no.
As you've clearly got something that fits your needs as do I by slowly making my own Winamp compatible player to run my old Winamp plug-ins (which were always closed source nor am I for or against OSS but it needs to be the dev that decides not external pressure) because I don't trust nor like what's happened with those that now own the brand.
Also source code is pointless without dev(s) & unless we're looking for AI to do all of the coding, whether the code is open or closed, the fleshy meat bag bashing the keyboard is still needed for the time being :)
Use what makes you happy & I'll keep making & using what makes me happy too :)
-dro